spectre-meltdown-checker: add updateScript

pkgs/by-name/sp/spectre-meltdown-checker/package.nix

@@ -1,10 +1,11 @@
 {
-  lib,
-  stdenv,
-  fetchFromGitHub,
-  makeBinaryWrapper,
-  coreutils,
   binutils-unwrapped,
+  coreutils,
+  fetchFromGitHub,
+  lib,
+  makeBinaryWrapper,
+  stdenv,
+  unstableGitUpdater,
 }:
 
 stdenv.mkDerivation (finalAttrs: {
@@ -18,6 +19,8 @@ stdenv.mkDerivation (finalAttrs: {
     hash = "sha256-m0f0+AFPrB2fPNd1SkSj6y9PElTdefOdI51Jgfi816w=";
   };
 
+  passthru.updateScript = unstableGitUpdater { };
+
   prePatch = ''
     substituteInPlace spectre-meltdown-checker.sh \
       --replace-fail /bin/echo ${coreutils}/bin/echo